With the clock ticking, Oakland Mayor Libby Schaaf is betting big that a combination of $600 million in private money from Ronnie Lott’s investment group, $200 million in public money and an equal amount from the National Football League will be enough to keep the stadium-hungry Raiders from moving to Las Vegas. At this point, the deal — which is being shuttled between the Oakland City Council and the Alameda County Board of Supervisors for approval — is just a broad outline of possible funding sources.